Method of controlling boiler

ABSTRACT

Disclosed herein is a method of controlling a boiler. In the boiler control method, the boiler is controlled depending both on a room temperature and on a return water temperature, whereby, unnecessary operation of the boiler is minimized. Further, the boiler is controlled depending on a desired room temperature and a corresponding return water temperature in a non-sleeping time zone, and the boiler is variably controlled, in the sleeping time zone, within a variable sleeping-time room temperature range and a variable sleeping-time return water temperature range. Moreover, in the present invention, a temperature control deviation is within ±0.5° C. and a return water temperature control deviation is within ±1° C. so that the room temperature and the temperature of a floor of the room can be maintained constant. Thus, energy consumption can be markedly reduced.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to Korean Application No. 10-2012-0063744 filed on Jun. 14, 2012, which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a method of controlling a boiler and, more particularly, to a boiler control method in which the boiler is controlled depending both on a room temperature and on a return water temperature, thus minimizing unnecessary operation of the boiler, and in which after twenty-four hours are divided into a non-sleeping time zone and a sleeping time zone by a sleep start time and a wake-up time, the boiler is controlled depending on a desired room temperature and a corresponding return water temperature in the non-sleeping time zone, and it is variably controlled, in the sleeping time zone, within a variable sleeping-time room temperature range and a variable sleeping-time return water temperature range which are lower than, respectively, the desired room temperature and the corresponding return water temperature by from 1° C. to 3° C., and in which a temperature control deviation is controlled within ±0.5° C. and a return water temperature control deviation is within ±1° C. so that the room temperature and the temperature of a floor of the room can be maintained constant, thus reducing energy consumption.

2. Description of the Related Art

Generally, as shown in FIG. 7, heating systems using a typical boiler include a boiler control unit 1 and a room controller 2. The boiler control unit 1 includes an MCU 1 a and a boiler drive unit 1 c which drives the boiler. The room controller 2 includes an MCU 2 a, a display 2 b, a temperature setting switch 2 c and a room temperature sensor 2 d. The boiler control unit 1 and the room controller 2 are connected to each other by interfaces 1 d and 2 e such as RS485 or the like.

In a conventional boiler control method, the boiler is controlled in such a way that the room temperature is controlled depending on a desired room temperature. The conventional boiler control method includes step S1 of turning on the boiler; step S2 in which a user sets a desired room temperature using the temperature setting switch 2 c of the room controller 2; step S3 of sensing a room temperature using the room temperature sensor 2 d of the room controller 2; step S4 of comparing the sensed room temperature with the desired room temperature in the MCU 1 a of the boiler control unit; step S5 of operating the boiler using the boiler drive unit 1 c when the sensed room temperature is lower than the desired room temperature; and step S6 of stopping the operation of the boiler using the boiler drive unit 1 c when the sensed room temperature is higher than the desired room temperature (refer to FIG. 8).

Here, the operation of the boiler means the operation of a heat generator and a circulation pump. The heat generator of the boiler refers to a burner in the case of an oil boiler or a gas boiler, a device which supplies combustion air into a combustion chamber and burns wood or charcoal in the case of a wooden charcoal boiler, and an electric heater in the case of an electric boiler. The circulation pump circulates hot water between the boiler and a heating pipe.

Typically, when the boiler is operated, heated hot water circulates between the boiler and the heating pipe. During this process, the floor of the room is heated by the hot water, and heat from the floor increases the room temperature.

The temperature of return water which returns to the boiler after having circulated through the heating pipe varies depending on the atmospheric temperature, specifications of the boiler, the location of the installed boiler or a structure to be heated, etc. Although the return water temperature reduces until the boiler is re-operated after the operation of the boiler has been temporarily stopped, it remains higher than the sensed room temperature.

Therefore, even when the sensed room temperature reaches the desired room temperature and the operation of the boiler is stopped, the return water temperature is still higher than the desired room temperature, that is, the return water still generates a sufficient amount of heat to heat the floor of the room and increase the room temperature.

However, in the conventional boiler control method, the boiler is operated or stopped only depending on the desired room temperature and the sensed room temperature, regardless of the return water temperature, resulting in an increase in energy consumption.

In other words, despite the fact that the return water generates a sufficient amount of heat to heat the floor of the room, if the sensed room temperature is lower than the desired room temperature, the boiler is operated regardless of the temperature of the return water, thus wasting energy.

Furthermore, in the conventional boiler control method, once the user sets a desired room temperature, the boiler is controlled only depending on the desired room temperature for twenty-four hours, that is, not only in a non-sleeping time zone but also in a sleeping time zone. Thereby, it may be difficult for the user to have a sound sleep due to an uncomfortably high room temperature. In addition, there is a problem of wasting energy.

For example, if the sleep start time is twenty-two o'clock and the wake-up time is six o'clock, the 24 hours of each day are divided into a non-sleeping time zone from six o'clock to twenty-two o'clock and a sleeping time zone from twenty-two o'clock to six o'clock. In this case, according to an experiment, even though the room temperature is set to be 25° C. and the room temperature is controlled to be 25° C., the user feel warm and comfortable in the non-sleeping time zone. However, in the sleeping time zone, if the room temperature is controlled to be 25° C., the user may feel the heat to such an extent that he/she sweats and is not able to have a sound sleep. In addition, energy consumption is unnecessarily increased.

Meanwhile, if the room temperature is controlled throughout the sleeping time zone to be lower than the room temperature of the non-sleeping time zone, the user may feel the cold when trying to fall sleep and have difficulty falling asleep. In addition, the user may also feel cold at the wake-up time, in which case the user will feel uncomfortably cold when they get out of bed.

Further, as shown in FIG. 10, in the heating system using the conventional boiler, a temperature control deviation is within ±1° C. Thus, when the return water temperature is lower than the desired room temperature Ts, the boiler is operated to increase the room temperature, but when the room temperature becomes the same as the desired room temperature Ts, the boiler is still operated, rather than being stopped, until the room temperature is higher than the corresponding return water temperature Ts by 1° C., that is, until the room temperature enters a state of Ts+1° C. Furthermore, after the boiler has been stopped, the room temperature is reduced, and even when the room temperature becomes the desired room temperature, the boiler is not operated and remains stopped until the room temperature becomes lower than the desired room temperature Ts by 1° C., that is, until the room temperature enters a state of Ts−1° C.

Therefore, in a section A1 in which the room temperature is higher than the desired room temperature Ts, additional energy is unnecessarily used. In a section A2 in which the room temperature is lower than the desired room temperature Ts, energy is insufficiently used. Because the additional energy consumption in the section A1 is greater than the shortage of energy use in the section A2, an energy loss is caused by a difference between the additional energy consumption and the shortage of energy use.

Moreover, in the section A2, there is a problem in that heat shortage makes the floor feel cooler.

SUMMARY OF THE INVENTION

Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a boiler control method in which the boiler is controlled depending both on a room temperature and on a return water temperature, thus minimizing unnecessary operation of the boiler, and in which after twenty-four hours are divided into a non-sleeping time zone and a sleeping time zone by a sleep start time and a wake-up time, the boiler is controlled depending on a desired room temperature and a corresponding return water temperature in the non-sleeping time zone, and it is variably controlled, in the sleeping time zone, within a variable sleeping-time room temperature range and a variable sleeping-time return water temperature range which are lower than, respectively, the desired room temperature and the corresponding return water temperature by from 1° C. to 3° C.

Another object of the present invention is to provide a boiler control method in which a temperature control deviation is controlled within ±0.5° C. and a return water temperature control deviation is within ±1° C. so that the room temperature and the temperature of a floor of the room can be maintained constant, thus reducing energy consumption.

In order to accomplish the above object, the present invention provides a method of controlling a boiler including a boiler control unit and a room controller, the method including: turning on the boiler; setting a room-temperature-corresponding return water temperature; setting a room-temperature-corresponding variable sleeping-time room temperature; setting a variable sleeping-time return water temperature corresponding to the variable sleeping-time room temperature; setting a desired room temperature using a temperature setting switch; sensing a room temperature using a room temperature sensor; sensing a return water temperature using a return water temperature sensor; determining a current time using a timer; and determining whether the current time is in a non-sleeping time zone or a sleeping time zone, wherein at the determining whether the current time is in the non-sleeping time zone or the sleeping time zone, when the current time is in the non-sleeping time zone, the boiler is controlled under a non-sleeping time zone control mode, and when the current time is in the sleeping time zone, the boiler is controlled under a sleeping time zone control mode, wherein the sleeping time zone control mode comprises comparing the room temperature sensed by the room temperature sensor with the variable sleeping-time room temperature, wherein at the comparing the room temperature with the variable sleeping-time room temperature, when the room temperature is higher than the variable sleeping-time room temperature, operation of the boiler is stopped, and when the room temperature is lower than the variable sleeping-time room temperature, the sleeping time zone control mode further comprises comparing the return water temperature with variable sleeping-time return water temperature, wherein at the comparing the return water temperature with variable sleeping-time return water temperature, when the return water temperature is lower then the variable sleeping-time return water temperature, the boiler is operated, and when the return water temperature is higher than the variable sleeping-time return water temperature, the operation of the boiler is stopped.

The non-sleeping time zone control mode may include comparing the room temperature sensed by the room temperature sensor with the desired room temperature. When the room temperature is higher than the desired room temperature, the operation of the boiler may be stopped. When the room temperature is lower than the desired room temperature, the non-sleeping time zone control mode may further include comparing the return water temperature with the room-temperature-corresponding return water temperature. When the return water temperature is lower than the room-temperature-corresponding return water temperature, the boiler may be operated, and when the return water temperature is higher than the room-temperature-corresponding return water temperature, the operation of the boiler may be stopped.

Furthermore, signal transmission between the boiler control unit and the room controller may be conducted by an interface RS 485, an interface power line modem, an interface RF or Bluetooth.

In addition, a temperature control deviation of the return water temperature sensor may be within ±1° C., and a temperature control deviation of the room temperature sensor may be within ±0.5° C.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIGS. 1 through 3 are block diagrams illustrating an embodiment of an apparatus for controlling a boiler to embody a method of controlling the boiler, according to the present invention;

FIG. 4 is a flowchart of a preferred embodiment of the boiler control method according to the present invention;

FIG. 5 is a chart showing a variable room temperature and a variable return water temperature by time zones depending on a desired room temperature according to the present invention;

FIG. 6 is a chart showing energy consumption by a temperature control deviation according to the present invention;

FIG. 7 is a block diagram of a boiler control apparatus proposed to embody a conventional boiler control method;

FIG. 8 is a flowchart of the conventional boiler control method;

FIG. 9 is a chart showing an room temperature and a return water temperature by time zones depending on a desired room temperature according to the present invention; and

FIG. 10 is a chart showing energy consumption by a temperature control deviation according to the conventional technique.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, a preferred embodiment of a method of controlling a boiler according to the present invention will be described in detail with reference to the attached drawings.

FIG. 1 illustrates an embodiment of a boiler control apparatus to embody the boiler control method according to the present invention. The boiler control apparatus includes a boiler drive unit 13 and a room controller 20. The boiler drive unit 13 includes an MCU 11, a return water temperature sensor 12 and a boiler drive unit 13 which drives the boiler. The room controller 20 includes an MCU 21, a display 22, a temperature setting switch 23 and a room temperature sensor 24.

Interfaces 14 and 24 connect the boiler control unit 10 and the room controller 20 to each other. The interfaces 14 and 24 may use RS 485 as shown in FIG. 1, a power line communication modem using a PLC (power line communication) as shown in FIG. 2, or a radio communication method using RF or Bluetooth.

Preferably, a sensor that has a temperature control deviation that is within ±0.5° C. is used as the room temperature sensor 24, and a sensor of which the temperature control deviation is within ±1° C. is used as the return water temperature sensor 12.

A first characteristic of the boiler control method according to the present invention is that the boiler is controlled depending on a room temperature, a desired room temperature and a corresponding return water temperature set in response to the room temperature, rather than being controlled depending on only the room temperature and the desired room temperature, whereby the operation of the boiler is minimized, thus reducing energy consumption.

A second characteristic of the boiler control method according to the present invention is that the 24 hours of each day are divided into a non-sleeping time zone and a sleeping time zone by a sleep start time and a wake-up time, the boiler is controlled depending on the desired room temperature and the corresponding return water temperature in the non-sleeping time zone, and the boiler is variably controlled, in the sleeping time zone, within a variable sleeping-time room temperature range and a variable sleeping-time return water temperature range which are lower than, respectively, the desired room temperature and the corresponding return water temperature by from 1° C. to 3° C., thereby reducing energy consumption.

A third characteristic of the boiler control method according to the present invention is that a temperature control deviation is within ±0.5° C. and a return water temperature control deviation is within ±1° C. so that the room temperature and the temperature of a floor of the room can be maintained constant, thus reducing energy consumption.

As shown in FIG. 4, the boiler control method according to the present invention includes: step S11 of turning on the boiler; step S12 of setting an room-temperature-corresponding return water temperature Tws; step S13 of setting a room-temperature-corresponding variable sleeping-time room temperature Trv; step S14 of setting a variable sleeping-time return water temperature Twv corresponding to the variable sleeping-time room temperature; step S15 of setting a desired room temperature Trs; step S16 of sensing a room temperature Tr; step S17 of sensing a return water temperature Tw; step S18 of determining a current time; step S19 of determining whether the current time determined at step S18 of determining the current time is in the non-sleeping time zone or the sleeping time zone; and controlling the boiler under a non-sleeping time zone control mode M1 when the current time is in the non-sleeping time zone or under a sleeping time zone control mode M2 when the current time is in the sleeping time zone.

At step S11 of turning on the boiler, after the boiler has been installed, the boiler is typically maintained in the turned-on state unless its use is not required for a long period of time. Therefore, separate manipulation is not required.

Furthermore, at step S12 of setting the room-temperature-corresponding return water temperature Tws, the room-temperature-corresponding return water temperature Tws is typically previously set, when the boiler is installed, depending on the specifications of the boiler or the conditions of a target to be heated, and is stored both in the MCU 11 of the boiler control unit 10 and in the MCU 21 of the room controller 20. Thus, there is no necessity for a user to separately set the room-temperature-corresponding return water temperature Tws.

Although it is preferable that the room-temperature-corresponding return water temperature Tws be set to a Trs+10° C., in other words, to a temperature which is higher than the desired room temperature Trs by 10° C., it may be adjusted depending on the specifications of the boiler or the location of the boiler or a structure to be heated.

At step S13 of setting the room-temperature-corresponding variable sleeping-time room temperature, the variable sleeping-time room temperature Trv is set within a temperature range which is lower than the desired room temperature Trs by from 1° C. to 3° C., that is, within a range from Trs−1° C. to Trs−3° C.

At step S14 of setting the variable sleeping-time return water temperature Twv corresponding to the variable sleeping-time room temperature, the variable sleeping-time return water temperature Twv is preferably set within a temperature range which is lower than the corresponding return water temperature Tws by from 1° C. to 3° C., that is, within a range from Tws−1° C. to Tws−3° C.

FIG. 5 is a chart showing the room temperature and the return water temperature by time zones when the desired room temperature Trs is 25° C. As shown in FIG. 5, referring to temperature distribution in the sleeping time zone ranging from twenty-two o'clock to six o'clock, the boiler is controlled such that at twenty-two o'clock, that is, the sleep start time, the room temperature is 25° C., which is the same as the desired room temperature Trs; at twenty-three o'clock, it is 24° C., which is lower than the desired room temperature Trs by 1° C.; at twenty-four o'clock, it is 23° C., which is lower than the desired room temperature Trs by 2° C.; from one o'clock to three o'clock, it is 22° C., which is lower than the desired room temperature Trs by 3° C.; at four o'clock, it is 23° C., which is lower than the desired room temperature Trs by 2° C.; at five o'clock, it is 24° C., which is lower than the desired room temperature Trs by 1° C.; and at six o'clock, that is, the wake-up time, it is 25° C., which is the same as the desired room temperature Trs. In other words, the boiler is controlled such that the room temperature is gradually reduced from the sleep start time to the middle of the night and then is gradually increased again from the middle of the night to the wake-up time until it becomes 25° C., which is the same as the desired room temperature Trs. The variable return water temperature Twv from the sleep start time to the wake-up time is controlled such that it has the same temperature variation value as that of the variable room temperature Trv, whereby the room is not too cold at the sleep start time so that the user can go to sleep in comfort, and it is not excessively hot in the middle of the night, allowing the user to continue having a sound sleep, and it is also not too cold at the wake-up time, so that the user can feel warm and comfortable when waking up. Furthermore, as shown in FIG. 5, the variable room temperature Trv in the non-sleeping time zone is controlled such that it is the same as the desired room temperature Trs. The variable return water temperature Twv in the non-sleeping time zone is controlled such that it has the same temperature deviation as that of the variable room temperature Trv.

At step S15 of setting the room temperature, the desired room temperature Trs refers to a room temperature Tr required by the user and is set by the temperature setting switch 23.

At step S16 of sensing the room temperature Tr, the sensed room temperature Tr refers to a room temperature Tr sensed by the room temperature sensor 24.

At step S17 of sensing the return water temperature Tw, the sensed return water temperature Tw refers to a temperature of water that is sensed by the return water temperature sensor 12 when water returns to the boiler after having been supplied from the boiler and having circulated through a heating pipe.

At step S18 of determining the current time, the current time is determined by a timer.

Step S19 of determining whether the current time is in the non-sleeping time zone or the sleeping time zone is needed to determine whether the boiler is controlled under the non-sleeping time zone control mode M1 or the sleeping time zone control mode M2.

In the non-sleeping time zone control mode, at step S21, a room temperature Tr sensed by the room temperature sensor 24 is compared with the desired room temperature Trs. If the room temperature Tr is higher than the desired room temperature Trs, the operation of the boiler is stopped, at step S40.

Meanwhile, if the room temperature Tr is lower than the desired room temperature Trs, the return water temperature Tw is compared with the corresponding return water temperature Tws, at step S22. As a result, if the return water temperature Tw is lower than the corresponding return water temperature Tws, the boiler is operated, at step S23. If the return water temperature Tw is higher than the corresponding return water temperature Tws, the operation of the boiler is stopped, at step S40.

As such, the boiler is controlled such that even though the room temperature Tr is lower than the desired room temperature Trs, only when the return water temperature Tw is lower than the corresponding return water temperature Tws is the boiler stopped, and if the return water temperature Tw is higher than the corresponding return water temperature Tws, the operation of the boiler is stopped. Therefore, the present invention can reduce energy consumption.

Here, although the operation of the boiler stops because the room temperature Tr is lower than the desired room temperature Trs, hot water that remains in the heating pipe can still heat the floor of the room and increase the room temperature, because the return water temperature Tw is higher than the corresponding return water temperature Tws.

In the sleeping time zone control mode, at step S31, a room temperature Tr sensed by the room temperature sensor 24 is compared with the variable sleeping-time room temperature Trv. If the room temperature Tr is higher than the variable sleeping-time room temperature Trv, the operation of the boiler is stopped, at step S40.

If the room temperature Tr is lower than the variable sleeping-time room temperature Trv, the return water temperature Tw is compared with the variable sleeping-time return water temperature Twv, at step S32. As a result, if the return water temperature Tw is lower than the variable sleeping-time return water temperature Twv, the boiler is operated, at step S33. If the return water temperature Tw is higher than the variable sleeping-time return water temperature Twv, the operation of the boiler is stopped, at step S40.

In this case, also, although the operation of the boiler stops because the room temperature Tr is lower than the desired room temperature Trs, hot water that remains in the heating pipe can still heat the floor of the room and increase the room temperature, because the return water temperature Tw is higher than the corresponding return water temperature Tws.

Furthermore, in the non-sleeping time zone control mode and the sleeping time zone control mode, the control deviation of the room temperature Tr is within ±0.5° C., and the control deviation of the return water temperature Tw is within ±1° C. Thus, as shown in FIG. 6, in a section A1 in which the room temperature Tr is higher than the corresponding room temperature Trs, unnecessary additional energy consumption occurs, and in a section A2 in which the room temperature Tr is lower than the corresponding room temperature Trs, energy is insufficiently used. Here, because the additional energy consumption in the section A1 is greater than the shortage of energy use in the section A2, an energy loss is caused by a difference between the additional energy consumption and the shortage of energy use. However, as can be understood from the oblique lined portions of FIGS. 6 and 10 comparing the boiler control method of the present invention to the conventional boiler control method, energy loss in the present invention is markedly reduced compared to that of the conventional boiler control method.

According to an experiment, when the room temperature and the return water temperature were reduced by 2° C., energy consumption was reduced by 20% per unit time.

As described above, a method of controlling a boiler having a boiler control unit and a room controller according to the present invention includes: the step of turning on the boiler; the step of setting a room-temperature-corresponding return water temperature; the step of setting a room-temperature-corresponding variable sleeping-time room temperature; the step of setting a variable sleeping-time return water temperature corresponding to the variable sleeping-time room temperature; the step of setting a desired room temperature using a temperature setting switch; the step of sensing a room temperature using a room temperature sensor; the step of sensing a return water temperature using a return water temperature sensor; the step of determining a current time using a timer; and the step of determining whether the current time is in a non-sleeping time zone or a sleeping time zone. At the step of determining whether the current time is in the non-sleeping time zone or the sleeping time zone, if the current time is in the non-sleeping time zone, the boiler is controlled under a non-sleeping time zone control mode, and if the current time is in the sleeping time zone, the boiler is controlled under a sleeping time zone control mode. The sleeping time zone control mode includes the step of comparing the room temperature sensed by the room temperature sensor with the variable sleeping-time room temperature. At the step of comparing the room temperature with the variable sleeping-time room temperature, when the room temperature is higher than the variable sleeping-time room temperature, the operation of the boiler is stopped, and when the room temperature is lower than the variable sleeping-time room temperature, the sleeping time zone control mode further includes the step of comparing the return water temperature with variable sleeping-time return water temperature. At the step of comparing the return water temperature with variable sleeping-time return water temperature, when the return water temperature is lower then the variable sleeping-time return water temperature, the boiler is operated, and when the return water temperature is higher than the variable sleeping-time return water temperature, the operation of the boiler is stopped. Thus, in the non-sleeping time zone, the room temperature and the return water temperature are controlled together depending both on the desired room temperature and on the corresponding return water temperature. Therefore, the room can be appropriately heated so that the user does not feel too cold or too hot. In the sleeping time zone, the room temperature and the return water temperature are respectively variably controlled together within a variable sleeping-time room temperature range that is lower than desired room temperature and within a variable sleeping-time return water temperature range. Therefore, the room can also be appropriately heated so that the user does not feel too hot while sleeping and is able to have a sound sleep. In the sleeping time zone, energy consumption can be reduced by a difference between the desired room temperature and the variable sleeping-time room temperature and by a difference between the corresponding return water temperature and the variable sleeping-time return water temperature.

Furthermore, in the present invention, the temperature control deviation of the room temperature sensor is within ±0.5° C., and the temperature control deviation of the return water temperature sensor is ±1° C. Thereby, a loss of energy can be markedly reduced.

Although the preferred embodiment of the present invention has been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. 

What is claimed is:
 1. A method of controlling a boiler comprising a boiler control unit and a room controller, the method comprising: turning on the boiler; setting a room-temperature-corresponding return water temperature; setting a room-temperature-corresponding variable sleeping-time room temperature; setting a variable sleeping-time return water temperature corresponding to the variable sleeping-time room temperature; setting a desired room temperature using a temperature setting switch; sensing a room temperature using a room temperature sensor; sensing a return water temperature using a return water temperature sensor; determining a current time using a timer; and determining whether the current time is in a non-sleeping time zone or a sleeping time zone, wherein at the determining whether the current time is in the non-sleeping time zone or the sleeping time zone, when the current time is in the non-sleeping time zone, the boiler is controlled under a non-sleeping time zone control mode, and when the current time is in the sleeping time zone, the boiler is controlled under a sleeping time zone control mode, wherein the sleeping time zone control mode comprises comparing the room temperature sensed by the room temperature sensor with the variable sleeping-time room temperature, wherein at the comparing the room temperature with the variable sleeping-time room temperature, when the room temperature is higher than the variable sleeping-time room temperature, operation of the boiler is stopped, and when the room temperature is lower than the variable sleeping-time room temperature, the sleeping time zone control mode further comprises comparing the return water temperature with variable sleeping-time return water temperature, wherein at the comparing the return water temperature with variable sleeping-time return water temperature, when the return water temperature is lower then the variable sleeping-time return water temperature, the boiler is operated, and when the return water temperature is higher than the variable sleeping-time return water temperature, the operation of the boiler is stopped.
 2. The method as set forth in claim 1, wherein the non-sleeping time zone control mode comprises comparing the room temperature sensed by the room temperature sensor with the desired room temperature, wherein at the comparing the room temperature with the desired room temperature, when the room temperature is higher than the desired room temperature, the operation of the boiler is stopped, and when the room temperature is lower than the desired room temperature, the non-sleeping time zone control mode further comprises comparing the return water temperature with the room-temperature-corresponding return water temperature, wherein at the comparing the return water temperature with the room-temperature-corresponding return water temperature, when the return water temperature is lower than the room-temperature-corresponding return water temperature, the boiler is operated, and when the return water temperature is higher than the room-temperature-corresponding return water temperature, the operation of the boiler is stopped.
 3. The method as set forth in claim 1, wherein the room-temperature-corresponding return water temperature is set to a temperature higher than the desired room temperature by 10° C., the room-temperature-corresponding variable sleeping-time room temperature is set to a temperature lower than the desired room temperature by from 1° C. to 3° C., and the variable sleeping-time return water temperature corresponding to the variable sleeping-time room temperature is set to a temperature lower than the room-temperature-corresponding return water temperature by from 1° C. to 3° C.
 4. The method as set forth in claim 1, wherein signal transmission between the boiler control unit and the room controller is conducted by an interface RS
 485. 5. The method as set forth in claim 1, wherein signal transmission between the boiler control unit and the room controller is conducted by an interface power line modem.
 6. The method as set forth in claim 1, wherein signal transmission between the boiler control unit and the room controller is conducted by an interface RF or Bluetooth.
 7. The method as set forth in claim 1, wherein a temperature control deviation of the return water temperature sensor is within ±1° C., and a temperature control deviation of the room temperature sensor is within ±0.5° C.
 8. The method as set forth in claim 1, wherein in the sleeping time zone control mode, the variable room temperature is varied in such a way that at a sleep start time, the variable room temperature is equal to the desired room temperature, is gradually reduced from the sleep start time to a predetermined time of a sleeping time zone, is maintained for a predetermined duration, is gradually increased again to a wake-up time, and then is equal to the desired room temperature at the wake-up time, and the variable return water temperature has a temperature variation value equal to a temperature variation value of the variable room temperature from the sleep start time to the wake-up time.
 9. The method as set forth in claim 2, wherein in the non-sleeping time zone control mode, the variable room temperature is equal to the desired room temperature during the non-sleeping time zone, and the variable return water temperature has a temperature deviation equal to a temperature deviation of the variable room temperature during the non-sleeping time zone. 